Fix tests

Raft.Test/TestServer.fs

@@ -87,7 +87,7 @@ module TestServer =
         (network.AllInboundMessages 0<ServerId>).Length |> shouldEqual 4
         (network.UndeliveredMessages 0<ServerId>).Length |> shouldEqual 0
 
-        cluster.Servers.[0].State |> shouldEqual ServerStatus.Leader
+        cluster.Servers.[0].State |> shouldEqual (ServerStatus.Leader 1<Term>)
 
         for i in 1..4 do
             cluster.Servers.[i].State |> shouldEqual ServerStatus.Follower
@@ -183,15 +183,12 @@ module TestServer =
                 cluster.SendMessageDirectly serverConsuming message
                 network.DropMessage serverConsuming messageId
 
-        (cluster.Servers.[0].State = Leader && cluster.Servers.[1].State = Leader)
-        |> shouldEqual false
-
-        (cluster.Servers.[0].State = Candidate && cluster.Servers.[1].State = Candidate)
-        |> shouldEqual false
-
-        ((cluster.Servers.[0].State = Leader && cluster.Servers.[1].State = Candidate)
-         || (cluster.Servers.[1].State = Leader && cluster.Servers.[0].State = Candidate))
-        |> shouldEqual true
+        match cluster.Servers.[0].State, cluster.Servers.[1].State with
+        | Leader _, Leader _ -> failwith "Unexpectedly had two leaders"
+        | Candidate _, Candidate _ -> failwith "Unexpectedly failed to elect a leader"
+        | Leader 1<Term>, Candidate 1<Term>
+        | Candidate 1<Term>, Leader 1<Term> -> ()
+        | s1, s2 -> failwithf "Unexpected state: %O %O" s1 s2
 
         for i in 2..4 do
             cluster.Servers.[i].State |> shouldEqual ServerStatus.Follower
@@ -233,8 +230,9 @@ module TestServer =
         let property (history : History) =
             apply history cluster network
 
-            (cluster.Servers.[0].State = Leader && cluster.Servers.[1].State = Leader)
-            |> shouldEqual false
+            match cluster.Servers.[0].State, cluster.Servers.[1].State with
+            | Leader _, Leader _ -> failwith "Unexpectedly elected two leaders"
+            | _, _ -> ()
 
             for i in 2..4 do
                 cluster.Servers.[i].State |> shouldEqual ServerStatus.Follower

Raft/InMemory.fs

@@ -0,0 +1,82 @@
+namespace Raft
+
+open System.Collections.Generic
+
+type Cluster<'a> =
+    internal
+        {
+            Servers : Server<'a> array
+            SendMessageDirectly : int<ServerId> -> Message<'a> -> unit
+        }
+
+    member this.SendMessage (i : int<ServerId>) (m : Message<'a>) : unit = this.SendMessageDirectly i m
+
+    member this.Timeout (i : int<ServerId>) : unit =
+        this.Servers.[i / 1<ServerId>].TriggerTimeout ()
+        this.Servers.[i / 1<ServerId>].Sync ()
+
+    member this.State (i : int<ServerId>) : ServerStatus = this.Servers.[i / 1<ServerId>].State
+
+    member this.ClusterSize : int = this.Servers.Length
+
+type Network<'a> =
+    internal
+        {
+            /// CompleteMessageHistory.[i] is the collection of all messages
+            /// ever sent to server `i`.
+            CompleteMessageHistory : ResizeArray<Message<'a>>[]
+            MessagesDelivered : HashSet<int>[]
+        }
+
+    static member Make (clusterSize : int) =
+        {
+            CompleteMessageHistory = Array.init clusterSize (fun _ -> ResizeArray ())
+            MessagesDelivered = Array.init clusterSize (fun _ -> HashSet ())
+        }
+
+    member this.AllInboundMessages (i : int<ServerId>) : Message<'a> list =
+        this.CompleteMessageHistory.[i / 1<ServerId>] |> List.ofSeq
+
+    member this.InboundMessage (i : int<ServerId>) (id : int) : Message<'a> =
+        this.CompleteMessageHistory.[i / 1<ServerId>].[id]
+
+    member this.DropMessage (i : int<ServerId>) (id : int) =
+        this.MessagesDelivered.[i / 1<ServerId>].Add id |> ignore
+
+    member this.UndeliveredMessages (i : int<ServerId>) : (int * Message<'a>) list =
+        this.CompleteMessageHistory.[i / 1<ServerId>]
+        |> Seq.indexed
+        |> Seq.filter (fun (count, _) -> this.MessagesDelivered.[i / 1<ServerId>].Contains count |> not)
+        |> List.ofSeq
+
+    member this.AllUndeliveredMessages () : ((int * Message<'a>) list) list =
+        List.init this.CompleteMessageHistory.Length (fun i -> this.UndeliveredMessages (i * 1<ServerId>))
+
+    member this.ClusterSize = this.CompleteMessageHistory.Length
+
+[<RequireQualifiedAccess>]
+module InMemoryCluster =
+
+    [<RequiresExplicitTypeArguments>]
+    let make<'a> (count : int) : Cluster<'a> * Network<'a> =
+        let servers = Array.zeroCreate<Server<'a>> count
+
+        let network = Network<int>.Make count
+
+        let messageChannelHold (serverId : int<ServerId>) (message : Message<'a>) : unit =
+            let arr = network.CompleteMessageHistory.[serverId / 1<ServerId>]
+            lock arr (fun () -> arr.Add message)
+
+        for s in 0 .. servers.Length - 1 do
+            servers.[s] <- Server (count, s * 1<ServerId>, InMemoryPersistentState (), messageChannelHold)
+
+        let cluster =
+            {
+                Servers = servers
+                SendMessageDirectly =
+                    fun i m ->
+                        servers.[i / 1<ServerId>].Message m
+                        servers.[i / 1<ServerId>].Sync ()
+            }
+
+        cluster, network

Raft/Raft.fsproj

@@ -10,6 +10,7 @@
       <Compile Include="Measures.fs" />
       <Compile Include="PersistentState.fs" />
       <Compile Include="Server.fs" />
+      <Compile Include="InMemory.fs" />
     </ItemGroup>
 
 </Project>

Raft/Server.fs

@@ -1,7 +1,5 @@
 namespace Raft
 
-open System.Collections.Generic
-
 /// Server state which need not survive a server crash.
 type VolatileState =
     {
@@ -471,82 +469,3 @@ type Server<'a>
         | ServerSpecialisation.Leader _ -> ServerStatus.Leader persistentState.CurrentTerm
         | ServerSpecialisation.Candidate _ -> ServerStatus.Candidate persistentState.CurrentTerm
         | ServerSpecialisation.Follower -> ServerStatus.Follower
-
-type Cluster<'a> =
-    internal
-        {
-            Servers : Server<'a> array
-            SendMessageDirectly : int<ServerId> -> Message<'a> -> unit
-        }
-
-    member this.SendMessage (i : int<ServerId>) (m : Message<'a>) : unit = this.SendMessageDirectly i m
-
-    member this.Timeout (i : int<ServerId>) : unit =
-        this.Servers.[i / 1<ServerId>].TriggerTimeout ()
-        this.Servers.[i / 1<ServerId>].Sync ()
-
-    member this.State (i : int<ServerId>) : ServerStatus = this.Servers.[i / 1<ServerId>].State
-
-    member this.ClusterSize : int = this.Servers.Length
-
-type Network<'a> =
-    internal
-        {
-            /// CompleteMessageHistory.[i] is the collection of all messages
-            /// ever sent to server `i`.
-            CompleteMessageHistory : ResizeArray<Message<'a>>[]
-            MessagesDelivered : HashSet<int>[]
-        }
-
-    static member Make (clusterSize : int) =
-        {
-            CompleteMessageHistory = Array.init clusterSize (fun _ -> ResizeArray ())
-            MessagesDelivered = Array.init clusterSize (fun _ -> HashSet ())
-        }
-
-    member this.AllInboundMessages (i : int<ServerId>) : Message<'a> list =
-        this.CompleteMessageHistory.[i / 1<ServerId>] |> List.ofSeq
-
-    member this.InboundMessage (i : int<ServerId>) (id : int) : Message<'a> =
-        this.CompleteMessageHistory.[i / 1<ServerId>].[id]
-
-    member this.DropMessage (i : int<ServerId>) (id : int) =
-        this.MessagesDelivered.[i / 1<ServerId>].Add id |> ignore
-
-    member this.UndeliveredMessages (i : int<ServerId>) : (int * Message<'a>) list =
-        this.CompleteMessageHistory.[i / 1<ServerId>]
-        |> Seq.indexed
-        |> Seq.filter (fun (count, _) -> this.MessagesDelivered.[i / 1<ServerId>].Contains count |> not)
-        |> List.ofSeq
-
-    member this.AllUndeliveredMessages () : ((int * Message<'a>) list) list =
-        List.init this.CompleteMessageHistory.Length (fun i -> this.UndeliveredMessages (i * 1<ServerId>))
-
-    member this.ClusterSize = this.CompleteMessageHistory.Length
-
-[<RequireQualifiedAccess>]
-module InMemoryCluster =
-
-    [<RequiresExplicitTypeArguments>]
-    let make<'a> (count : int) : Cluster<'a> * Network<'a> =
-        let servers = Array.zeroCreate<Server<'a>> count
-
-        let network = Network<int>.Make count
-
-        let messageChannelHold (serverId : int<ServerId>) (message : Message<'a>) : unit =
-            let arr = network.CompleteMessageHistory.[serverId / 1<ServerId>]
-            lock arr (fun () -> arr.Add message)
-
-        for s in 0 .. servers.Length - 1 do
-            servers.[s] <- Server (count, s * 1<ServerId>, InMemoryPersistentState (), messageChannelHold)
-
-        let cluster =
-            {
-                Servers = servers
-                SendMessageDirectly =
-                    fun i m ->
-                        servers.[i / 1<ServerId>].Message m
-                        servers.[i / 1<ServerId>].Sync ()
-            }
-
-        cluster, network